Power does diminish with distance due to I2R losses. For cables using AC, there are also reactive losses. To compensate, the cable companies boost the voltage a

Power does diminish with distance due to I2R losses. For cables using AC, there are also reactive losses. To compensate, the cable companies boost the voltage at both ends (30-500 kV) of the cable such that the repeater at the middle of the span has enough juice to operate properly. And, yes, separate cables, or wire bundles, carry the power and ground.